dm error: add discard support

Add io_err_io_hints() and set discard limits so that the zero target
advertises support for discards.

The error target will return -EIO for discards.

This is useful when the user combines dm-error with other
discard-supporting targets in the same table; without dm-error
support, discards would be disabled for the whole combined device.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Tested-by: Milan Broz <gmazyland@gmail.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

diff --git a/drivers/md/dm-target.c b/drivers/md/dm-target.c
index 26ea22b..97a75f3 100644 (file)
--- a/drivers/md/dm-target.c
+++ b/drivers/md/dm-target.c
@@ -119,6 +119,7 @@ static int io_err_ctr(struct dm_target *tt, unsigned int argc, char **args)
         * Return error for discards instead of -EOPNOTSUPP
         */
        tt->num_discard_bios = 1;
+       tt->discards_supported = true;
 
        return 0;
 }
@@ -145,6 +146,13 @@ static void io_err_release_clone_rq(struct request *clone,
 {
 }
 
+static void io_err_io_hints(struct dm_target *ti, struct queue_limits *limits)
+{
+       limits->max_discard_sectors = UINT_MAX;
+       limits->max_hw_discard_sectors = UINT_MAX;
+       limits->discard_granularity = 512;
+}
+
 static long io_err_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
                long nr_pages, enum dax_access_mode mode, void **kaddr,
                pfn_t *pfn)
@@ -154,13 +162,14 @@ static long io_err_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
 
 static struct target_type error_target = {
        .name = "error",
-       .version = {1, 5, 0},
+       .version = {1, 6, 0},
        .features = DM_TARGET_WILDCARD,
        .ctr  = io_err_ctr,
        .dtr  = io_err_dtr,
        .map  = io_err_map,
        .clone_and_map_rq = io_err_clone_and_map_rq,
        .release_clone_rq = io_err_release_clone_rq,
+       .io_hints = io_err_io_hints,
        .direct_access = io_err_dax_direct_access,
 };